A 74 vintage 350 is going to have crapola heads on it and will have very low static compression. Early smog heads are a mess both for efficiency and performance. The low static compression may or may not be an issue -- really depends on if you intend to add compression to the intake.
Go with the crate and, if you plan to live on the highway a lot -- either replace the trans or find an overdrive unit for the puppy.